Background: Alopecia areata (AA) is associated with multiple comorbidities and shares a similar inflammatory signature with dementia. The great negative psychosocial impact of AA may result in poor social engagement, a typical risk factor for dementia. However, little is known about the association between AA and dementia. Methods: Via the Taiwan National Health Insurance Research Database, 2,534 patients with AA (International Classification of Diseases, 9th Revision, Clinical Modification code: 704.01) aged ≥ 45 years and 25,340 controls matched for age, sex, residence, income, dementia-related comorbidities, systemic steroid use, and annual outpatient visit were included between 1998 and 2011 for investigation of subsequent dementia from enrollment to the end of 2013. After controlling for potential confounders, stratified Cox regression analysis on each matched pair was applied to assess the dementia risk between the AA and control groups. Results: Patients with AA were more likely to develop any dementia (adjusted hazard ratio [aHR] = 3.24; 95% CI, 2.14-4.90), Alzheimer's disease (aHR = 4.34; 95% CI, 1.45-12.97), and unspecified dementia (aHR = 3.36; 95% CI, 2.06-5.48) than the control cohort. Stratification analysis by age and sex revealed increased risks of any dementia and unspecified dementia in both age groups (ie, < 65 and ≥ 65 years) and both sex groups and increased risks of AD in male patients and in those with age at dementia onset ≥ 65 years. Sensitivity analyses after exclusion of the first year or first 3 years of observation showed consistent findings. Conclusions: Patients with AA had a higher risk of developing dementia. Further studies are needed to elucidate the underlying pathophysiology between AA and dementia risk.
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